Mercury switch relay



Feb. 25, 1941. c. E. GEHRAND MERCURY SWITCH RELAY Filed Sept. 25, 1939 2Sheets-Sheet l I I lz'zz/(antor: Clary/7x021? G/Q/ZPMLZ MM1-Q Feb. 25,1941. E GE 2,232,880

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Glovioosly in writing oommesclol specifications IE will be understoodWillow skilled in line fol" relays of this kind, scilximmi and maximumart the following description given in com values are cfteo given foroperate and release necilon with the drawings illustrates and deilmes,these values representing lime intervals scribes preferred embodimentsof this invention which must be met regardless of the relative and thatvariations may be made in the details positioning of the switch parts(i. e, in stable of oonstx'uctlon wiilolli del fi g f the sp itequilibrium or not) at the instant that the conend s pe of the inventionas defined in the dlclon of the electrical circuit through the relay mwinding is Q The minimum Values are Front contact relay (Figs. 1 and 2)so usually specified to prevent an immediate change in circuit conditionin the event of subnormal The relay 511mm in Figs- 1 and 2 has in Brecycnng conditions, and t maximum values eral the followingcharacteristics: Normally open are usually given to hold the operationof the contact (1. e., afront contact switch); slow make, relay toreasonable cycles or to some other speretarded brea and substantially quOpera-t8 clal operating condition. reset. The switch illustrated isdesigned to make 55 or bridge contacts in 3.5 seconds. and to break oropen contacts in 0.6 second.

The relay employs a time delay element comprising a gas leak in athimble associated with one electrode and a second time delay elementcomprising a mercury cup leak associated with the same electrode. Theswitch has a quick or automatic reset when used in certain recyclingcircuits and when the mercury leak is faster than the gas leak.

The relay as shown in Figs. 1 and 2 comprises a coil ll provided withspaced poles ii and I2 within which the relay switch generallydesignated II is suitably mounted. The switch it comprises a switchenvelope i4 preferably or low expansion boro-silicate glass through thebase oi which lead-ins II and i1, preferably 01' molybdenum or tungsten,are pinch-sealed. The leadins extend upwardly into the switch envelopeand are provided with insulating sleeves ii, the sleeve ll surroundingthe lead-in ll being interrupted to expose a portion II oi the lead-inI! to the mercury an i. in the envelope H. The two leads II and I!terminate in the electrode portions Ii and 22, respectively, which areadapted to be bridged and unbridged by appropriate manipulation oi themercury an II in a manner to be described.

A glass thimble generally designated as I! is telescoped over theelectrode portion 2i and is fined to the upper end of the stem ll asindicated at II. The thimble is provided with a relatively large opening21 at one side to permit the mercury to pass freely to and from thethimble except only as the movement of the mercury is retarded, when theopening 21 is closed, by the action a time delay element II in the upperend oi the thimble. This element consists of a gas pervious cylinder 0!ceramic material, preferably Alundum Grade RA 98, bonded by iusion orother suitable means into an opening provided in the upper end of thethimble. The cylinder. therefore. oil'ers a predetermined impedance tothe flow 0! gas therethrough in accordance with the exposed portion ofthe cylinder whenever the'mercury in the envelope completely covers theopening 21. The cylinder 2| is, oi course, impervious to mercury.

The electrode portion ll of the lead-in ll extends above its insulatingsleeve ll into the interior of the thimble II where it is surrotmded bya ceramic cup Ii bonded to the upper end of said insulating sleeve. The.cup forms a reservoir tor a small pool of mercury which is always incontact with the electrode portion 2| and permits the bridging oi theelectrodes II and 22 to be accomplished by a mercury to mercury contact.

Fused to the upper portion of the sleeves II is an insulating sleeve orcylinder 33 which extends upwardly surrounding the electrode portion 22and the major portion oi the thimble II. ,This sleeve is open at itsupper end and is provided with a mercuryleakor opening in its sideadjacent the lower end of opening 21 thus iorm-' ing a mercury leakagetime delaycup. The opening is always below the mercury level and formost uses and circuits it is advantageous to have time delay action ofthe mercury leakage through the opening 84 shorter than that oi the gasleakage through llv The mercury on I! within the envelope is manipulatedby a magnetically controlled plunger or displaoer generally designatedas II and which comprises an iron sleeve I. telesooped over a glass orceramic cylinder 33. This iron sleeve comprises the armature and may besplit along one side if desired for operation with alternating current.The sleeve or armature is guided for movement within the envelope by a.guide washer 31 adjacent each end of the armature and held thereon bycoiled springs 38 which have their end convolutions telescoped andfrictionally engaging the end portions of the armature 35. These springsalso serve to cushion the armature within the glass envelope.

The switch envelope i3, before being sealed, is completely evacuated andthen filled with a suitable inertgas such as helium, hydrogen, or thelike, or a mixture oi such gases.

Operation 0] front contact relay The two final positions of stableequilibrium oi the switch parts of the front contact type areillustrated in Figs. 1 and 2, and the movement and operation of theswitch from one position to the other is as follows:

Assume that the switch parts are in stable equilibrium with the coildeenergized as shown in Fig. l and that the coil is then suddenlyenergized. Immediately upon energization of the coil the displacer 35 islowered to the position of Fig. 2. Because the opening 34 in the sleeve33 is submerged in the mercury illl when the parts are in stableequilibrium and remains submerged as the displacer is lowered, theopening has no eflect upon the normal operate time. In other words, whenthe displacer moves from the Fig. 1 position to the Fig. 2 position, themercury till throughout the entire envelope first rises to a position atapproximately the top edge of the opening 21 in thimble 28 after whichthe mercury in the outer portion of the envelope rises to slightly"above line ll of Fig. 2 while the mercury within the thimble, remainstemporarily at the lower level due to compression of the gas in the topportion oi the thimble. This compressed gas prevents the immediate riseof the mercury in the thimble and, accordingly, prevents bridging oi thecontacts 2i and 22. Due to the pressure diilerential in the envelope andthe thimble, the gas in the thimble slowly leaks through the poroussleeve II, at a predetermined rate that is dependent upon the porosityoi the sleeve. thus permitting the mercury to rise slowly in the thimbleuntil it finally flows into the ceramic cup Ii, bridges with the mercuryin the cup Ii, and thus completes the circuit through the switch. If therelay coil remains energized, the mercury then levels oil to theposition shown in Fig. 2.

The time that is required for the inside mercury level to reach the topmargin of the ceramic cup II and make contact with the mercury thereinis determined solely by the impedance which the time delay element orcylinder 2| in the thimble oilers to the passage oi gas escaping fromthe thimble. The exposed portion or this element and its porosity arechosen so as to eiiect a total lapse oi time such that the time requiredfor the mercury to rise from the upper edge 01 the opening 21 to theupper edge oi the ceramic cup Ii and into contact with the mercury poolin the cup is equal to the specified normal operate time of the relaywhich, in the switch illustrated, is 3.5 seconds.

Assume now that the switch parts are in stable equilibrium with thecontacts bridged and the .coil energized, as shown in Fig. 2. and thatthe coil is then suddenly deenergized. Immediately the displacer risesto the Fig. 1 position due to its buoyancy and the outside mercury dropsto a position just above the opening 21. The mercury within the thimbleis momentarily retained at a level just above the top of the cup II andin position to bridge the electrodes due to the presence of the cylinder33, which causes a mercury seal to be retained around the opening 21.The mercury, however, in the cup 33 tends to level of! with the mercuryoutside of that cup, by flowing through the opening or leak 34, but themercury within the thimble 26 is held in contact with the mercury in theelectrode cup 2| by the surface tension of the mercury and the partialvacuum in the thimble. This condition can obtain for a limited period oftime only, and if the breaking of the circuit is not to be madedependent upon uncontrollable variables, it is quite important for thetime delay action of the mercury leakage element 34 to be shorter thanthe corresponding ac-' tion of the gas leakage element 28. In theillustrated relay, the specified normal release time is 0.6 seconds.This means that 0.6 seconds is required for the mercury level to dropfrom the top of the cup 33 to the top 01 the opening 21, and as soon asthis happens, gas enters the thimble through the opening 21, effectivelyby-passing the gas leakage element 28, and causing the mercury level inthe thimble 26 to immediately fall to the position shown in Fig. 1, thusbreaking the circuit through the switch.

The use of the mercury cup time delay in combination with the gas timedelay on the fixed thimble makes it possible to obtain certain relaycharacteristics that would otherwise be imobtainable. With such anarrangement, a front contact relay can be provided having a normaloperate time (the time necessary for the mercury to rise from stableequilibrium above the opening 21 to bridging condition) oi ten seconds,for example, after which the mercury levels of! at a point higher thanbridging level. This can be obtained by the proper selection of the gasleak 28 and the distance between the top of the opening 21 and the edgeof the mercury cup 3|. The same relay can have a normal release time(the time necessary for the mercury to drop from stable equilibriumafter bridgin to unbridging position) of two seconds, for example, byproperly selecting the distance between the inner top wall of thethimble 26 and the upper edge of the mercury cup 3|. By making theopening 24 of proper size and the wall 33 of appropriate height, themercury seal may be maintained at the upper margin 0! opening 21 forslightly more than two seconds, after which the seal is broken and themercury contact at the cup 3| is opened. The relay, therefore, ischaracterized in this instance by having a normal operate recycling timeof three seconds, or thereabouts and a normal release recycling time 01'thirteen seconds, or thereabouts, with normal operate and release timesof ten and two seconds, respectively. The foregoing characteristicscould not be obtained without the combined action of two time delayelements.

The relay described in connection with Figs. 1 and 2 may be used toadvantage in a recycling circuit, such as is disclosed in Fig. 3,because diicharacteristics, or the kind which the present relaypossesses.

Reterrlng to Fig. 3, a load is illustrated at 45 which is controlled bythe combined action of a mercury time delay relay l3, illustrateddiagrammatically and having the time delayv characteristics previouslydescribed (3.5 seconds to close and .6 second to open with quick operatereset) and a fast acting or quick make and quick break, back contactrelay 4'. The relay I3 is, of course, of the front contact type and hasits coil connected across the continuously energized leads 41, but inseries with the contacts 48 of the relay 46. The coil of the quickacting relay 48 is con nected to the leads 41 through the contacts 2|and 22 of the mercury relay I! as is also the load 45.

Upon energizing the leads 41, the relay I3 is energized through thenormally closed back contacts 48 and closes contacts 2| and 22 after thepredetermined normal operate time oi 3.5 seconds. Closing of thecontacts 2| and 22 energizes relay 48 and the load 45. Relay 48, however, is a quick make, quick break relay which, immediately uponenergization, opens its contacts 48. This results in deenergization ofthe operating coil of relay B which reopens contacts 2| and 22, after acertain minimum release time for the relay I! which, in the presentinstance, is 0.6 second.

Stated in other words, energization of leads 41, it sustained asufiicient length of time, causes the load 45 to be operated for a giveninterval of time, namely, the minimum release time for the relay II, butthis operation of the load occurs only after a given time interval haselapsed sub-- sequent to the energization of leads 41, the time beingthe normal operate time of the relay II. Thus, the normal operate timeof the relay I! can be selected and the normal release time can bechosen so as to give desired operating and non-operating periods to theload.

In addition to these characteristics, relay |3 has substantially quickoperate reset characteristic in the illustrated circuit for reasonsgiven below so that if the leads 41 are first energized and thendeenergized before the contacts 2| and 22 have had an opportunity toclose, the prescribed normal operate time will elapse between the secondenergization of the leads 41 (it not within 0.6 second) and the closingof the contacts 2| and 22. This is true of the relay IS in theillustrated circuit when the mercury leak is substantially greater thanthe gas leak so that the tormer controls the normal release time. Thisresults in a quick operate reset so that normal operate time will beobtained even under subnormal operate recycling conditions.

Operation of the relay I! when in the circui arrangement of Fig. 3 maybe explained as follows:

Assume that the coil II has, been energized, thus causing the displacerto be lowered from the Fig. 1 to the Fig. 2 position, but that the coilis deenergized before the mercury has had time to bridge electrodes 2|and 22, after which the coil II has been reenergized (but not before 0.6second has elapsed). As soon as the coil is deenergized, the displacerrises. The mercury in the outer portion of the envelope does notcontinue to rise with the displacer, but drops. Due to the tact that themercury ieab, is greater than the gas leak, the mercury rapidly dropslow the upper edge of the opening 21 and new mits gas to enter thiinbleand restore iii mercuiy to the level of Fig. 1 so that, uponreenergization of the coil II, a full normal operate period will takeplace, even under subnormal operate recycling conditions described.

Back contact relay-Fios. 3 and 4 The relay shown in Figs. 4 and 5 has,in general, the following characteristics: Normally closed contact; slowmake, retarded break; and substantially quick release reset. Here again,the switch illustrated is designed to make or bridge the contacts in 3.5seconds, and to break or open the contacts in 0.6 second. Also, therelay employs two time delay elements comprising a gas leak in thethimble and a mercury leak associated with the plunger or displacer.

The relay shown in Figs. 4 and 5 is similar to that shown in Figs. 1 and2, except that the parts are somewhat dlfl'erently proportioned, themain difference being that the electrodes and thimble are positionedlower in the envelope by shortening the stem II. The elements of therelay are substantially the same and are therefore given the samereference characters.

Briefly, the relay comprises a coil I. provided with spaced poles II andI2 within which the glass envelope I4 is positioned. Leads I8 and I!extend upwardly through the sleeve or stem II and have electrodeportions 2| and 22 which are adapted to be bridged and unbridged byappropriate manipulation of the mercury fill ii.

A glass thimble 25 is fused to the upper end of the stem and surroundsthe electrode 2|, being provided at its lower end with an opening 21 andat its upper end with a time delay gas pervious element II. A mercuryleakage time delay cup is provided by a cylinder 33 which is also fusedto thestem II and is provided with the mercury leakage opening 34. Inmost cases,

it is desirable to make the mercury leak greater than the gas leak.

The mercury nil I8 is manipulated by a magnetleally controlled plungeror displacer 35 comprising an iron sleeve or cylinder 36 guided for 5longitudinal movements in the envelope by spider washers 31. The sleeveis cushioned by springs 38 as previously described.

Operation 0/ back: contact relay The two final positions of stableequilibrium of the switch parts oi the rear contact switch relay areillustrated in Figs. 4 and 5, and the movement and operation of theswitch from one position to the other is as follows:

Assume that the switch parts are in stable equilibrium with the contactsbridged and the coil deenergized, 'as shown in Fig. 4, and that the coilis then suddenly energized. Immediately upon energization of the coil,the dis- '0 placer I! is raised to the position of Fig. 5 and themercury outside of the cylinder 13 drops to a point above the opening34. The mercury within the thimble, however, cannot drop immediately dueto the mercury seal retained around the opening 21 by reason oi! thewall 33, and the partial vacuum created in the upper portion of thethimble. Therefore, lowering of the mercury within the thimble 25 isretarded temporarily until suflicient mercury has passed -1 through theleak 34 to lower the level of the mercury below the upper margin of theopening 21, whereupon gas enters the thimble, and the mercuryimmediately drops and opens the switch contacts. The period required forthe mercury to lower. in the thimble suflieiently to open the contactsis controlled by the mercury time delay leak through the opening 34 andis the normal operate time which, in the illustrated relay. is 0.6second. The mercury finally levels of! and the parts assume thepositions of stable equilibrium illustrated in Fig. 5.

Assume now that the parts are in stable equi librium, as shown in Fig.5, with the contacts open or unbridged and the coil energized and that,under these conditions, the coil is suddenly deenergized. The plunger ordisplacer immediately drops into the mercury which immediately rises tothe level of the lower margin 01' the opening 21. When the mercury hasreached this level, the outer mercury being unrestricted continues torise, but the mercury within the thimble cannot rise immediately due tothe gas pressure created in the upper portion of the thimble. The gaspressure in the upper portion of the thimble then being higher than thegas pressure in the envelope, the pressures tend to equalize by leakageof the gas through the time delay element 28. This leakage permits themercury to rise slowly in the thimble until it finally flows into theceramic cup 3! and bridges the contacts. The time that is required {orthe inside mercury to reach the top level of the ceramic cup 3| andbridge the contacts is determined solely by the impedance which the timedelay element or cylinder 28 in the thimble offers to the passage 01'gas escaping therethrough, and this time is the normal release time.After the contacts are bridged, the mercury levels oil to the level ofFig. 4. In the relay illustrated, the positioning of the parts has beenso selected and the porosity of the gas leak so chosen that the normalrelease time is 3.5 seconds.

Like the front contact switch or relay, the back contact switch may beused in a recycling circuit in which the relay is recycled through itsown contacts if such operation is desired. Such a circuit would be likethat of Fig. 3 in principle, but, of course, somewhat different indetail, as will be obvious to those skilled in the art.

It will be apparent to those skilled in the art that, in both front andback contact iorrns oi the invention, any limitation in quick resetcharacteristics of the switches may be avoided by the use of theswitches in circuits in which the recycling of the relay is controlledby the relay contacts and by making the mercury leak appreciably greateror faster than the gas leak, i. e. by making the time delay caused bythe mercury leak appreciably less than the time delay caused by the gasleak.

The combination of a gas time delay in the fixed thimble with themercury time delay in the mercury cup makes it possible to obtain timedelays on both the opening and closing of the contacts with a muchgreater range oi flexibility than it is otherwise possible to obtain.The combination of two time delays is 01 even greater advantage when thetime delays on both make and break have to be held to very close limits,due to the fact that the individual time delays or leaks may be adjustedindependently without one materially ailecting the other.

Another way to describe the function of the two time delay elements isto say that by their use, the relay is able to have time delay actionboth when closing and when opening the circuit through the switch, andyet have a quicker reset action than would be possible had only one timedelay element been used.

We claim:

1. In a mercury switch relay having prescribed operatingcharacteristics, the combination of a relay coil, a switch associatedwith the coil, said switch comprising an envelope, spaced electrodes inthe envelope, a mercury till, a ho]- low displacer responsive to thecoil for shitting the mercury level, and cooperating time delay elementsassociated with one of said electrodes to delay the movement of mercurywith relation to said electrode upon a change in the condition of theelectrical circuit through the coil, one '0! said time delay elementscomprising a gas leakage device fixed with respect to one of saidelectrodes and arranged to control the movement of mercury toward saidelectrode and the other one of said time delay elements comprising amercury cup provided with a restricted wall opening for the timedpassage of mercury arranged to control the movement of mercury away froman electrode, whereby the switch is characterized by a delayed make andadeiayed break of the circuit through the electrodes.

2. In a mercury switch relay having prescribed operatingcharacteristics, the combination oi a relay coil, a switch associatedwith the coil, said switch comprising an envelope, spaced electrodes inthe envelope, a mercury till, a hollow displacer responsive to the coilfor shifting the mercury level, and cooperating time delay elementsassociated with one of said electrodes to delay the movement of mercurywith relation to said electrode upon a change in the condition of theelectrical circuit through the coil, one of said time delay elementscomprising a gas leakage device fixed with respect to one of saidelectrodes and arranged to control the movement of mercury toward saidelectrode and the other one of said time delay elements comprising amercury cup extending over a portion of said gas leakage device andprovided with a restricted wall opening for the timed passage of mercuryarranged to control the movement of mercury away from said electrode,whereby the switch is characterized by a delayed make and a delayedbreak of the circuit through the electrodes.

3. In a mercury switch relay having pre scribed operatingcharacteristics, the combination of a relay coil, a switch associatedwith the coil, said switch comprising an envelope, spaced electrodes inthe envelope, a mercury fill, a hollow displacer responsive to the coilfor shifting the mercury level, cooperating time delay elementsassociated with one of said electrodes to delay the movement of mercurywith relation to said electrode upon a change in the condition of theelectrical circuit through the coil, one of said time delay elementscomprising a gas leakage device fixed with respect to one of saidelectrodes and the other comprising a relatively fixed mercury leakagedevice, and means including at least one oi said time delay elements forinsuring that, once the electrodes have been bridged with mercury, theywill remain bridged for at least a brief period of time.

4. In a mercury switch relay having prescribed operatingcharacteristics, the combination of a relay coil, a switch associatedwith the coil, said switch comprising an envelopeyspaoed electrodes inthe envelope, a mercury fill, a hollow displacer responsive to the coilfor shifting the mercurylevel, cooperating time delay elementsassociated with one of said electrodes to delay the movement of mercurywith relation to said electrode upon a changeinthe condition of theelectrical circuit through the coil, one of said time delay elementscomprising a gas leakage device fixed with respect to one oi saidelectrodes and the other comprising a relatively fixed mercury leakagedevice, and means including at least one of said time delay elements forcausing the switch to have substantially quick operate resetcharacteristics.

5. In a mercury switch relay having prescribed operatingcharacteristics, the combination of a relay coil, 9. switch associatedwith the coil, said switch comprising an envelope, spaced electrodes inthe envelope, a mercury 1111, a hollow displacer responsive to the coilfor shitting the'mercury level, cooperating time delay olel5 mentsassociated with one of said electrodes to delay the movement of mercurywith relation to said electrode upon a change in the condition oi. theelectrical circuit through the coil, one 0! said time delay elementscomprising a gas leakage device fixed with respect to one 0! saidelectrodes and the other comprising a relatively fixed mercury leakagedevice, and means including at least one of said time delay elements forcausing the switch to have substantially quick release resetcharacteristics.

6. In a mercury switch relay having prescribed operatingcharacteristics, the -combination of a relay coil, a switch associatedwith the coil, said switch comprising an envelope, spaced electrodes inthe envelope, a mercury fill, a hollow displacer responsive to the coilfor shifting the mercury level, and cooperating time delay elementsassociated with one 01' said electrodes to delay the movement of mercurywith relation to said electrode upon a change in the condition or theelectrical circuit through the coil, one of said time delay elementscomprising a fixed thimble telescoped over one of said electrodes andhaving a gas leakage device at its upper end and the other comprising amercury cup extending around and above the bottom of said thimble andprovided with a restricted wall opening for the timed passage ofmercury, the gas leakage device associated with said thimble beingrelatively slow 45 in its action as compared to the mercury passageassociated with the cup.

'7. In a. mercury switch relay having prescribed operatingcharacteristics, the combination of a relay coil, a switch associatedwith the coil, said switch comprising an envelope, spaced electrodes inthe envelope. a mercury fill, a hollow displacer responsive to the coilfor shifting the mercury level, and cooperating time delay elementsassociated with one of said electrodes to delay the movement of mercurywith relation to said electrode upon a change in the condition of theelectrical circuit through the coil, one oi said time delay elementscomprising a fixed thimble mounted over one of said electrodes andhaving an opening for the passage oi mercury and a top gas leakagedevice. and the other comprising a mercury cup extending around andabove said side opening provided with a restricted wall opening for thetimed passage of mercury, and said displacer being telescoped over themercury cup whereby upward movement of the displacer causes an immediatedrop in the mercury column within said cup.

8. In a mercury switch relay having prescribed operatingcharacteristics, the combination of a relay coil, a switch associatedwith. the

' coil, said switch comprising an envelope, spaced electrodes in theenvelope, a mercury fill, a hollow displacer responsive to the coil forshifting the mercury level. and cooperating time delay elementsassociated with one of said electrodes to delay the movement of mercurywith relation to said electrode upon a change in the condition of theelectrical circuit through the coil, one oi said time delay elementscomprising a gas leakage device fixed with respect to one of saidelectrodes and arranged to control the movement of mercury toward saidelectrode and the other one of said time delay elements comprising amercury cup extending over a portion 01' said gas leakage device andprovided with a restricted wall opening for the time passage of mercuryarranged to control the movement of mercury away from said electrode,said time delay element in said cup being faster in effect than said gasleakage time delay element, whereby the switch is characterized by adelayed make and a delayed break 0! the circuit through the electrodesand is further characterized by having a substantially quick reset atleast for one direction of movement of the mercury.

CLARENCE E. GEHRAND.

